I have never finished!

Help, every time I masturbate, I always get to a great point of it (I almost never finger myself) but then my clit get extremely sensitive to touch I can’t handle it, but I still feel like I’m not done, and it doesn’t feel good at all, it’s very frustrating and I’m left with a strange feeling down there. I have been masturbating for about a year now. The same thing happens when my bf gives me oral sex, I feel the same way. (I have never had intercourses before) I really take my time when I masturbate, I have tried so much. Same thing with my boyfriend we do it a lot, and it feels amazing! But I just don’t get to an ending point, help what is this I’m feeling.